(a) Field of the Invention
The invention relates to an apparatus and method for manufacturing molten irons, and more particularly to an apparatus and method for manufacturing molten irons that supplies oxygen and water to a fluidized-bed reactor for increasing a temperature in the fluidized-bed reactor to thereby manufacture molten irons.
(b) Description of the Related Art
The iron and steel industry is a core industry that supplies the basic materials needed in construction and in the manufacture of automobiles, ships, home appliances, and many of the other products we use. It is also an industry with one of the longest histories that has advanced together with human progress. In an iron foundry, which plays a pivotal roll in the iron and steel industry, after molten iron (i.e., pig iron in a molten state) is produced using iron ore and coal as raw materials, steel is produced from the molten iron and is then supplied to customers.
Approximately 60% of the world's iron production is realized using the blast furnace method developed in the 14th century. In the blast furnace method, cokes produced using iron ore and bituminous coal that have undergone a sintering process as raw materials are placed in a blast furnace, and oxygen is supplied to the furnace to reduce the iron ore to iron to thereby manufacture molten iron. The blast furnace method, which is a main aspect of molten iron production, requires raw materials having a hardness of at least a predetermined level and grain size that can ensure ventilation in the furnace. Coke in which specific raw coal that has undergone processing is needed as a carbon source to be used as fuel and a reducing agent. Also, sintered ore that has undergone a successive compacting process is needed as an iron source. Accordingly, in the modern blast furnace method, it is necessary to include raw material preparation and processing equipment such as coke manufacturing equipment and sintering equipment. Therefore, not only is it necessary to obtain accessory equipments in addition to the blast furnace, but equipment to prevent and minimize the generation of pollution in the accessory equipment is needed. The amount of investment, therefore, is considerable, ultimately increases manufacturing costs.
In order to solve these problems of the blast furnace method, significant effort is being put forth in iron foundries all over the world to develop a smelting reduction process that produces molten irons by directly using fine coal as fuel and as a reducing agent, and also directly using fine ores, which are used in over 80% of the world's ore production, as an iron source.
As an example of such a smelting reduction process, U.S. Pat. No. 5,584,910 discloses a method of manufacturing molten iron that directly uses fine coals and fine ores. A method is disclosed in this patent for producing a molten pig iron or molten steel preliminary product from a charge material that partially includes fine iron ores. The fine iron ores are directly reduced into sponge irons in at least one fluidized-bed reactor, and the sponge iron is melted in a melting region by supplying carbon carriers and an oxygen containing gas. Reduced gas that is generated in this process is provided to the fluidized-bed reactors, then is exhausted as an exhaust gas after undergoing reaction.
When compared to the conventional blast furnace method, since the above method for manufacturing molten iron uses fine iron ores and fine coals instead of lump ores and cokes, the advantage is realized in which the range of grain sizes of raw coal is wide. Further, equipment stoppages and re-starting are easy. However, as a result of using the fine iron ores as raw material and also using multiple stages of fluidized-bed reactors, it is not easy to adjust an inner state of the fluidized-bed reactors, and in particular, an inner temperature thereof.
Accordingly, in order to adjust an inner temperature of the fluidized-bed reactors, a method is used in which a separate combustion chamber and burner are provided to an exterior of the fluidized-bed reactors to thereby increase the temperature of a gas supplied to the fluidized-bed reactors. However, when the reaction gas that is increased in temperature passes through a dispersing plate provided to induce uniform gas flow in the fluidized-bed reactors, ore particles contained in the reaction gas form a compound having a low melting point such that the dispersing plate becomes blocked, thereby making it impossible to perform fluidized bed reduction process.